Electromagnetic relay



April 2, 1946. F, E, WOOD 2,397,635

ELECTROMAGNETI C RELAY Filed Feb. 26, M 343 0 FIGS INVENTOR. FREDRIG E. WOOD ATTOR NEY Pmma Apr. 2, 1946 ELECTROMAGNETIC RELAY Fredric E. Wood, Oak Park, 111., minor to Automatic Electric Laboratories, Inc., a corporation of Delaware Application February 2a, 1943, Serial No. 477,220

8 Claims (01. 200-104) The present invention relates in generalto electromagnetic devices and, more particularly, to electromagnetic devices of the relay type.

An electromagnetic device of the relay type conventionally comprises a field structure including a core provided with a winding, a movable armature carried by the field structure, and one or more sets of switch springs operativel associated with the armature.

It is the object 01' the present invention to provide an improved electromagnetic relay of the type described which is light in weight, diminutive in size, economical in construction, and yet reliable, long wearing, and positive 'in operation.

Another object of the invention is to provide in an electromagnetic relay an improved multicontact switch spring arrangement which positively insures electrical contact between each pair of associated contacts carried by the switch springs and which accommodates equalization of the contact pressure between associated contacts.

A further object of the invention is to provide in an electromagnetic relay an improved mounting arrangement for the relay armature including an anti-vibration means which positively eliminates vibration of the armature mass from an external source, such as is encountered when the relay structure is mounted in an airplane, tank, automobile, train, and other vibratory machinery eithermobile or stationary, without subjecting the armature or its bearing to such stress or strain that the normal operating characteristics of the relay are altered thereby. a

The objects set forth above are in part realized in accordance with one feature of the Present invention by providing an electromagnetic relay which comprises one or more sets of switch springs, each set comprising one or more so called armature springs, which are movable under control of the relay armature, and one or more so called make or break springs, engageable with or disengageable from said movable armature springs under control of said armature, wherein each of the armature springs comprises a relatively long flexible portion and is provided with two spacedapart and independently flexible portions and a plurality of contacts carried by the flexible portions, and wherein each of the make or break springs comprises a relatively short stifl portion and is provided with two spaced-apart and independently flexible portions and a plurality of contacts carried by the flexible portions, the contacts carried. by the flexible portion of the armature spring cooperating with the contacts carried by More particularly, each of the break or make springs is formed oi flat metallic stock and is provided with a base end and a free end comprising a relatively short stifl portion to iacilitate maximum ease of adjusting the relative position thereof, and a pair-oi very flexible branches which, al-

though of unequal cross section and unlike shape, equalize the contact pressure between cooperating contacts of armature springs.

Each of the armature springs is formed of flat metallic stock and is provided with a base end and a free end comprising a relatively long flexing portion to i'acilitate'maximum ease of adjusting the pressure of the spring against the armature or cooperating spring, and minimum operating power from the relay to move the armature, thereby to effect a change in the relative positions of the contacts on the armature springs with respect to the cooperating contacts of the make or break springs.

The two independently flexible portions provided in the armature spring are formed by an elongated slot provided adjacent the free end thereof and the two flexible portions provided in the make or b eak spring are formed by an elongated L-shaped slot provided at the free end thereof. Also, the contacts respectively carried by the flexible portion of the spring are carried thereby at points along the lengths of the flexible portions whereat the flexible portions have a maximum movement with respect to the base portion of the springs, thereby to insure self equalization of contact pressure between the respective engaging contacts when the contacts carried by the flexible portion of the armature springs are respectively forced into engagement with the contacts respectively carried by the flexible portions of the associated make or break springs.

Furthermore, the means for moving the armature springs comprises an operating member carried by each armature spring adjacent the free end and intermediate the two flexible portions thereof and an arm including the relay armature operating to engage the operating member.

According to another feature of the invention, one or more spring sets are assembled, independently of'the relay. to a non-magnetic clamping plate provided with a comparatively long armature bearing surface whereby the armature and its associated pivot pin is rotatably secured to the field structure by the mere act of securing the spring set or sets tothe field structure. The clamping plate is also of greater width than the free end of the heel piece so that there is sumthe flexible portions of the make or break springs. cient space between the arm or arms of the armature and the sides the heel piece to insure minimum loss oil grower as a result of magnetic leakage therebetweoh. hon -magnetic bearing is also provided between the spring set clamping plate and the held structure to provide a bearing surface for the pivot pin.

Relays having armatures of the pivot pin. type have been extehsh ly used in telephone systems and have proved very satisfactory. however, it has been found that relays or" this type when sub=- jected to coasts. 5 vi .tion from an external source are subject stresses not present in the normal use of thee relays. Tests have shown that the vibration caused excessive wear on either the bearing surface for the pivot pin or upon the pivot pin itself, thereby interfering with the normal operating characteristics of the relay. The analysis of this excessive wear shows that it re= sults from at least two different types of motion.

The armature exerts a turning movement proportional to its mass and the rate and the direction of the vibratiom. This tends to produce oscillations of the armature transverse to the axis or the pivot in at a rate corresponding to the vibration rate.

It the vlbratiorieare in a plane which includes the pivot pin and the center oi mass or the airma time, a force is exerted which tends to maize pivot pic. chatter lu hearing at a rate propor= tional to the vibration is a feature of the oreseut invention to elimihate the above me. tiohed motions of the arzna= ture produced by external vibration of the relay by exerting a twisting action upon the armature and its associated pivot pin by means or" a flexible spring, included in the spring set, which spring applies a relatively light pressiue to the armature at a point betweeh the armature backstop and the bearing This light pressure maintains the pivot pin in constant engagement with the bearing surface and eliminates the possibility of the above mentioned objectionable vibratory motion between the pivot pin and the pivot pin bearing. Such a pressure is sufficient to prevent both the transverse motion and the chatter motion referred to above without adversely affecting the operating and releasing characteristics of the relay when the same is energized and deehergiaed.

@ther object and features of the present illvention will be apparent by reference to the following speciilcatio r taken in connection with the accompanying drawing, which:

Fig. l is a side View oi an electromagnetic relay constructed and arranged in accordance with the present invention;

Fig. 2 is a right end view of the relay illustrated in Fig. 1;

Fig. 8 is an exploded perspective view of the electromagnetic relay illustrated in Fig, 1;

Fig. 4 is an enlarged sectional view showing the arrangement tor pivotally supporting the relay armature;

Fig. .5 is a plan view of an electromagnetic relay constructed and arranged in accordance with the present invention but modified to accommodate two separate switch spring sets;

Fig. 6 is a right end view of the modified relay illustrated in Fig. 5.

Referring now more particularly to Figs. 1 to i, inclusive, of the drawing, the electromagnetic relay there shown comprises a field structure including a longitudinally extending core element it provided with a winding ill, a substantially l.-= shape magnetic heel piece i l, secured to the core aeoaoss element it, by means or a screw it, and a movable magnetic armature l6 pivotally mounted upon the outer end of the heel piece ill and cooperating with the core element l2.

As best shown in. Figs. 1 and 3, the armature it) carries a pair or spaced-apart upwardly extending ears it provided with aligned holes therein and an operating arm ll. A pivot pin. 25) is inserted into the aligned holes and the outer ends oi the pivot pin 23 are flanged over in order to rigidly secure the pivot pic. 21] to the armature it. The operating arm il extends along the side of the heel piece and parallel thereto, and is provided at the end thereor" with an inwardly extending operating projection llo which overlaps the upper suriace oi the heel piece i l and normally rests upon a hon-magnetic rivet 22, secured to and ex= tending upwardly from the upper surface of the heel piece it.

In order to provide bearing surlace for the pivotal armature, a non-magnetic bearing plate is, formed or bronze or the like, is carried upon the upper surface of the heel piece i adjacent to the outer end thereof, and the pivot pin it is rotatably held against the upper suriacc oi the bearing plate 08 in a transverse pivot pin receiving slot 23 iorroed in the bottom surface oi the clamp- V plate 13. *l'he arrangement for securing the armature ii": in pivotal relationship with the heel piece i l and the core 32 will described 113. do tail hereinafter.

To facilitate assembly of. the electromagnetic relay, the switch spring set 25 is assembled inde pendcntly of the relay structure itself, and, after assembly, is secured to the heel piece l l together with the bearing plate and the armature With this arrangement diderent combinations of switch spring sets may be carried in stool: by a relay manufacturer in order to meet the customers requirements for different numbers of springs as well as difiereht combinations of make and break switch springs.

More particularly, the switch spring set comprises a plurality of individual switch springs 2t,

27, and and armature restoring and re straining spring 29 arranged in super imposed re lationshlp. Each of the switch springs comprise a base end and a free end and is provided with a cantilever mounting at its base end. Also, the springs are insulated from each other and from the clamping plate at their base ends. The arrangement for assembling and insulating the base ends of the spring set comprises a clamping plate iii, the plurality of insulators 23, tubular insulators 23, an end plate 35], the individual springs ll, 28, the restoring spring 29, and a retaining screw 3 i. More particularly, the retaining screw 31] is inserted through the center tubular insulator is and threaded into the tapped hole 3 1' in the clamping plate is to securely clamp the springs and insulators between the clamping plate is and the end plate 3-1] in assembled relationship, until it is desired to fasten the spring set, by means of mounting screws 32, upon the heel piece id.

In order to assemble the spring set 25 upon the heel piece ill, the bearing plate it is placed thereon with the three clearance holes therein in alignment with the three holes provided in the heel piece M. The armature i5 is then held in place with the pivot pin 25, in engagement with the pivot pin receiving slot 25! provided in the bottom surface of the clamping plate it, as is clearly shown in the enlarged view Fig. 4, and the holes in plate ll) placed in alignment with the holes provided in the heel piece it and the bear- 8,897,885 ing plate l8. Screws 22 are then inserted through the two outside holes in the end plate 30 and threaded into the tapped holes 28 in the heel iece H to securely fasten the spring assembly 28, the pivot pin bearing plate l8, the armature l5, and theheel piece H together into a unitary structure. In order to permit adjustments of the air gap between the armature i and the relay core l2, slotted holes, are providedin the clamping plate l8 and the bearing plate l8, and the two outside tubular insulators 24 are pro- 'vided with clearance holes therein which are slightly greater in diameter than the diameter of the mounting screw 32.

The switch springs 28, 21, and 28 as disclosed, comprise a so-called break-make spring combination in which the armature spring 21 is adapted to be moved out of eng ement with the cooperating break spring 28 into engagement with the cooperating make spring 28. In order to facilitate maximum ease of adjustment of the relative position of springs 28 and 28 with respect to the armature spring 21, these springs are provided with a relatively short stiff portion extending from the base end thereof, and a pair of very flexible branches 84 and 35. The flexible portions 34 and 35 of springs 28 and 28 carry adjacent the free end thereof a pair of metallic contacts.

Although the pair of flexible branch portions of springs 28 and 28 are of unequal cross-section and of unlike shape, they provide, in combination with the associated relatively long, but flexible, armature spring 21, an arrangement which equalizes the contact pressure between cooperatwelded to its associated flexible portion of the springs at a point along the length of the flexible portion of the associated spring, whereat the flexible portion has a maximum movement with respect to ,the base end or relatively-still body portion of its associated spring, thereby to insure self-equalization of the contact pressure between the respective engaging contacts, either when the contacts of the armature spring 21 and the contacts of the break spring 28 are'in engagement, or when the contacts of the armature spring 21 and the contacts ofthe make spring 28 are in engagement.

In order to facilitate movement of the armature spring 21, with respect to the associated break and make springs, a substantially cupshaped metallic flxture 48 is securely fastened by 1 welding or the like to the lower surface of the curved operating portion 39 of the armature spring 21. A substantially cylindrical insulating operating element, or bushing 4|, is arranged within the fixture 40 and irictionally secured in place by the side wall thereof. Preferably, one

ing contacts of associated cooperating springs. Since the branch portions 34 and 35 arevery flexible, the position to which the stiff portions of these springs are adjusted with respect to the cooperating armature spring 21 may be approximate rather than accurate.

The armature spring 21 is provided with a relatively long, flexible portion, as compared with the relatively short, stifi portion of the cooperating make and break springs 28 and 28, to facilitate maximum ease of adjusting the pressure of this spring against the break spring 28, or, if no break spring such as 28 is provided, against the operating projection l1a, whereby minimum operating power is required of the relay to overcome the tension of this spring in order to disengage the armature spring 21 from the cooperating break spring 28 and to move it into engagement with the cooperating make spring 26. In the event no break spring 28 is required, the armature restoring spring 29 may be omitted in which case the bushing 4| 0n the spring 21 may directly engage the operating projection Na.

More particularly, the armature spring 21 is provided with an elongated longitudinally extending slot 36 formed therein adjacent the free end thereof, which slot provides the armature spring the spring to cooperate respectively with the pair of contacts provided on the bottom side of the end of the bushing 4| is provided with an inverted frusto-conical section which is inserted into the cup-shaped fixture 48, and then the side wall of the flxture is spun orpressed down into firm engagement with the conical side wall of the received section of the bushing 4|. The specific construction and arrangement described above is disclosed in the copending application of Fredric E. Wood, Serial No. 459,121, flied September The bushing 4| cooperates directly with the armatur restoring and restraining spring 29, and contacts on the armature spring 21 are adapted to be urged thereby out of engagement with the cooperating contacts on the break spring 28 into engagement with the cooperating contacts on the make spring 26. 'More particularly, when the winding i3 is energized, the armature I5 is rotated about the pivot pin 20 in a counterclockwise direction as viewed in Fig. 1, thereby to cause the armature It to be moved from its normal position to its operated position. When this occurs, the pivot pin 20 rotates in the transverse pivot pin receiving slot 2| formed in the bottom side of the clamping plate I9, the adjacent upper surfacegof the bearing plate l8 serving also as a bearing surface therefor. Also, at this time the operating projection Ha, carried by the arm l1 of the armature I5, acts upon the armature restoring spring 29 and the bushing 4|, and consequently, upon the armature spring 21. Accordin ly, the armature spring 21 is flexed, whereby the normally engaged contacts of the associated break spring 28 are disengaged, and the normally disengaged contacts of the associated make spring 28 are engaged by the associated cooperating contacts oi. the armature spring 21.

It is to be noted that the non-magnetic rivet 22 underlying the operating projection l1a prevents the projection mentioned from sticking to the adjacent surface or the heel piece It, clue to leakage of magnetic flux therebetween.

In order to prevent objectionable play between the pivot pin 20 and the bearing surfaces, comprising the transverse pivot pin receiving slot 2| and the bearing plate I 8, when the entire relay structure is vibrated from an external source, the relatively long flexible restoring spring 29 is lightly. tensioned against the upper surface of the operating projection arm I'Ia between the point where the bottom surface thereof rests upon make spring 28. Each of the spring contacts is the rivet 22 and the point where the arm l'l tion of the armature from an external source,

either transverse to the axis of the pivot pin or parallel to the axis of the Pivot pin.

In view of the fact that the armature restor= ing spring 29 applies its pressure to the operating projection Ha at a point remote from the pivot pin 20 and also at a point remote from fulcrum -22, considerably less pressure is required to over= come any tendency of the armature 65 to vibrate from an external source than would he required if the pressure was applied directly to the pivot pin itself. By actual test, it has been found that a very small percentage of the pressure required at the pivot pin to prevent vibration of the armature, is required when the pressure is applied to the operating projection H: at the remote end of the armature E in the manner shown.

It may be well to mention at this time that in the event that the break spring is omitted from the combination of switch spring set 25, the necessity of providing a separate armature restoring spring, such as spring 29, is eliminated, because the function of restoring the armature and applying the necessary pressure to the openating projection i'ia may then be performed by the armature spring Z'l.

Referring now to Figs. 5 and 6 of the drawing,

there is shown therein an electromagnetic relay, constructed and arranged in accordance with the relay constructure disclosed in Figs. l to ill-=- clusive, but modified to accommodate two separate switch spring sets. More particularly, the left-hand switch spring set 42 of Fig. 6 is identical to the switch spring set 25, except that the clamping plate 38 and the bearing plate iii are increased in width to accommodate both the lefthand switch spring set t2 and the right-hand switch spring set 63. Furthermore, the armature of the modified relay is provided with left and right hand armature arms t t and and as= sociated operating projections M d and its, in-.

stead of a single armature arm. El and a single operating projection lid as is provided in the relay disclosed in-Figs. l to e inclusive. [a nonmagnetic rivet fiii is provided, underlying the operating projection the, to prevent the armature operating projections Mo. and d from sticking I to the adjacent heel piece and to provide a iul crum about which the armature tends to twist and take up objectionable play in the same mannor as has been previously described.

It is to be noted, however, that the switch spring set t3 does not include an armature restoring and restraining spring such as spring 2a. A spring of this type is included, however, in the switch spring set it and provides the necessary pressure to the armature in order to automatically take up any play which might occur between the armature pivot pin and its bearing surfaces, and thereby prevents vibration of the armature from. an external source.

Having described the construction and assembly of the relay, the utility and purpose of the invention will be set forth to enable the assaess same to be more understood and appreciated.

It is well known that in mass production of a large number of parts which are to be assembled together, manufacturing tolerances within certain limits are resorted to in order to speed up production and to reduce the costs of manufacturingsuch parts. For example, since relay parts are manufactured in large numbers, manufacturing tolerances are allowed on both the pivot pin 20 and the pivot pin receiving slot H of the relay shown in the drawing. It has been found that in manufacturing the pivot pin 20, it may be oversize or undersize from the desired diameter, and that the pivot pin receiving slot 22 may also be oversize or undersize from the desired diameter. In view of the above, it can be seen that a minimum diameter pivot pin may be assembled in a maximum diameter pivot pin receiving slot. Consequently, there may be considerable play between the pivot pin and the pivot pin receiving slot. In the event that a relay is assembled with a pivot pin or minimum diameter mounted in a pivot pin receiving slot having a maximum diameter, and the relay is mounted on an object subject to vibration, such as may be encountered in an airplane, tank, automobile, train and other vibratory machinery, either mobile or stationary, the vibrations of the armature will cause a gradual wearing of the pivot pin and the pivot pin receiving slot, and thereby gradually increases the play between these parts to such an extent that the operating characteristics of the relay will be materially affected.

According to the present invention, the light pressure applied to the operating projection lid of the armature E5 causes the pivot pin to be twisted in the pivot pin receiving slot to constantly maintain the parts in engagement with each other and thereby take up any play which may occur as a result of manufacturing tolerances.

It is to be noted that the armature spring 2i swings about a pivot point which is located approximately adjacent the point where the spring protrudes from the side of the securely clamped base end of the spring. When the armature spring Z'E is actuated responsive to the movement of the armature arm ill the contacts thereon swing through a rather large arc and consequently wipe across the contacts on the cooperating make or brealr. springs 26 and 28 in a line longitudinal to the length of the armature spring. Furthermore, since the portion of the maize and break. springs 26 and 28 extending from the end of the securely clamped base ends of the I springs is relatively short and still as compared by the associated armature spring 2i, and consequently wipes across the associated contact thereof at right angles to the wiping action caused by the movement of the armature spring 2T. In addition, the L-shape branch portion 35 of the make and break springs 26 and 29;, extending at; right angles to the relative shortstifi portion, swings through a first rather short are with the base of the L forming the pivot point therefor together with a second rather short arc, with the junction of the short-stiff portion and one leg or the it forming the pivot point therefor. Consequently, the contact on the L-shape portion of spring 26 or 28 wipes acros the associated contact on the armature spring 21 at an angle intermediate the Wiping action caused by movement of the contacts on the armature spring 2'! and th wiping action caused by movement of the contact on the flexible branch portion 3 3. From the foregoing it will be noted that the wiping action which occurs between the contact on the branch portion 34 and the associated contact on the armature spring 2'! are at right angles to one another, thereby insuring positive contact engagement therebetween and also maximum movement therebetween for the purpose of dislodging any dust particles. Furthermore, it will be noted that the wiping action which occurs between the contact on the branch portion 35 and the associated contact on the armature spring 21 are at an angle from one another, which angle is intermediate the wiping motion occurring between the contact on the branch portion 34 and the associated contact on the armature pring 21. The wiping action therebetween also insures positive contact engagement between th contact on branch portion 35 and the associated contact on the armature spring 21 and also considerable movement therebetween for the purpose of dislodging dust particles.

Having fully described the invention, what is considered to be new and desired to have protected by Letters Patent is specifically pointed out in the following claims.

What is claimed is:

1. In a relay including a magnet and a heel piece secured thereto, an armature therefor including a pivot pin, means for supporting said pivot pin on said heel piece whereby said armature is rotatably supported on said heel piece, said armature including an operating arm extending transversely across said heel piece, a fulcrum on said heel piece cooperating with said operating arm, and means for applying pressure to said operating arm at a point removed from said fulcrum and said armature pivot pin whereby any play existing between said pivot pin and said supporting means is eliminated.

2. In a switching device, an armature, a pivot pin secured to said armature, a heel piece, a pivot pin bearing plate, means securing said bearing plate to said heel piece, means in said bearing plate rotatably securing said pivot pin on said heel piece providing a bearing surface for said pivot pin, said armature including an operating arm, a fulcrum for said operating arm providing an air gap between said operating arm and said heel piece to prevent magnetic leakage therebetween, and means for applying a light pressure to said operating arm at a point removed from said fulcrum whereby aid pivot pin is twisted in said bearing "to take up any play existing between said pivot pin and said bearing surface.

3. In a relay including a magnet and a heel piece secured thereto, an armature therefor including a pivot pin, a switch spring set, means for rotatably mounting said pivot pin between said switch spring set and said heel piece whereby said armature is rotatably supported on said heel piece, said armature including an operating arm for operating said switch spring set, a fulcrum for said operating arm, and means including said switch spring set for applying pressure to said operating arm at a point removed from said fulcrum and said armature pivot pin to create a torque whereby any play existing between said pivot pin and said rotatabl mounting means is eliminated.

4. In a switching device, a spring set including a plurality of spring contacts, an armature, a pivot pin secured to said armature, a heel piece, a pivot pin bearing plate, means securing said spring set to said bearing plate, means securing said spring set and said bearing plate to said heel piece, means in said bearing late rotatably securing said pivot pin on said heel piece providing a bearing surface for said pivot pin, said armature including a pring set operating arm, a fulcrum for said operating arm providing an air gap between said operating arm and said heel I piece to prevent magnetic leakage therebetween,

and means including said spring set for applying a light pressure to said operating arm at a point removed from said fulcrum whereby said pivot pin is twistedin said bearing to take up any play existing between said Pivot pin and said bearing surface.

5. In a relay including a maget and a heel piece secured thereto, a unitary structure comprising an armature and a pivot pin, a spring set comprising a plurality of springs and a clamping plate secured together, a pivot pin bearing surface in said clamping plate, means for securing said spring set to said heel piece thereby to'secure said unitary structure to said heel piece with said pivot pin in rotatable relationship with said bearing surface, and means including one of said plurality of springs for applying pressure to said armature at a point removed from said pivot pin, to thereby tilt said pivot pin in said bearing to maintain saidpivot pin in constant engagement with said bearing surface and to prevent movement of said armature except when said magnet is being energized and deenergized.

6. In a relay including a magnet core and a heelpiece secured thereto, an L-shaped armature, means including a pivot pin and a bearing for rotatably supporting aid armature on said heelpiece, an operating arm on said armature, extending in a plane parallel with said pivot pin and transversely across said heelpiece, a non-' magnetic member on said heelpiece cooperating with the free end of said operating arm to provide an air gap between said operating arm and heelpiece and for limiting the air gap between said armature and core, and a restoring spring on said heelpiece for applying pressure to said operating arm at a point intermediate said member and bearing whereby said member acts as a fulcrum to twist said pivot pin 'in said bearing to eliminate any existing play between said pivot pin and bearing.

FREDRIC E. WOOD. 

